Heretofore, a mold type composition of frictional material using asbestos as matrix fibers and a phenolic resin as a binder has generally been employed as composition of frictional materials for use in brake linings. This conventional molded type composition of frictional material for use in brake linings contains as a binder an organic substance which is thermally decomposed at high temperature, and therefore fadings, i.e., lowering of the frictional coefficient compared to the required coefficient, are resulted. Recently, the brake linings using glass fibers or aromatic polyamide fibers instead of asbestos have been reported, as disclosed in Japanese Patent Laid-Open Publications Nos. SHOWA 53-130742 and SHOWA 56-16579. Since aromatic polyamide fibers are organic substances as well as a phenolic resin, fadings are resulted when aromatic polyamide fibers are thermally decomposed in braking. Also, Japanese Patent Laid-Open Publication No. SHOWA 57-205473 discloses the cryolite powder is blended in a composition of frictional material for use in brake linings an inorganic grain.
As described above, for the conventional composition of frictional material for use in brake linings containing asbestos as matrix fibers, there has been known such problems that the friction coefficient is substantially low or fadings are resulted when brakes are frequently operated. While, a mold type composition of frictional material for use in brake linings containing aromatic polyamide fibers as matrix fibers and a phenolic resin as a binder, possibly lowers the anti-fading performance because of containing a large quantity of the organic substances.
The object of this invention is to provide a new molded type composition for use in brake linings by using polyparaphenylene terephthalamide as matrix fibers of a superior anti-fading performance and a phenolic resin as a binder in order to exhibit a high friction coefficient and a lower wear ratio.